Current technologies for nuclear magnetic resonance (NMR) sensors use the same antenna to generate high-energy radio-frequency (RF) excitation pulses and to receive and detect the echo signals induced by the high-energy RF excitation pulses. Thus, NMR sensors face the problem of decoupling a receiver circuit driving a low noise amplifier (LNA) receiving the echo signal provided by the antenna from undesirable ringing effects produced by transient high voltage in the antenna after excitation pulse transmission. Current solutions rely on dampening resistor controlled by a switch to dampen a residual excess voltage in the antenna circuit from a few volts (Vs) to nano-volts (nVs). The resistor adds undesirable noise if left during reception, hence turned off during the reception. Fast turn off of switch like devices in general can induce undesirable ringing in the antenna due to charge injection effects. To quench the ringing effects induced in the antenna due to switching action current technologies introduce a resistor-capacitance (RC) delay circuit in the gate driver of the switching device. This slows down the turn off of the switch and hence induces less ringing in to the antenna. However, use of RC circuits alone to increase the turn-off time of the switching device tends to delay the ability of the NMR sensor to receive and process echo signals by at least a few hundreds of micro-seconds (μs).
In addition to the undesirable reduction in time resolution, these delays adversely limit data collection rate of the NMR sensor. These factors result in undesirably slow NMR receivers.
In the figures, elements having the same or similar reference numerals refer to the same or similar function, or step, unless otherwise noted.